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<b>let </b><font color="Maroon">p</font> be   <a href="pre_topc.html#NM2">Point</a> of <span class="p1">(<span class="default"><a href="euclid.html#K15">TOP-REAL</a> 2</span>)</span>;<br/><b>let </b><font color="Maroon">C</font> be   <a href="struct_0.html#NM2">Subset</a> of <span class="p1">(<span class="default"><a href="euclid.html#K15">TOP-REAL</a> 2</span>)</span>;<br/>



<a NAME="E1:22"/>
( <span class="p1">(<span class="default"><a href="jordan18.html#K1" target="_self">North-Bound</a> <font color="Maroon">p</font>,<font color="Maroon">C</font></span>)</span> <a href="euclid.html#K21">`1</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">p</font> <a href="euclid.html#K21">`1</a>  &amp; <span class="p1">(<span class="default"><a href="jordan18.html#K2" target="_self">South-Bound</a> <font color="Maroon">p</font>,<font color="Maroon">C</font></span>)</span> <a href="euclid.html#K21">`1</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">p</font> <a href="euclid.html#K21">`1</a>  )
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E2:22"/>
 <a href="topreal1.html#K3">LSeg</a> <span class="p1">(<span class="default"><a href="jordan18.html#K1" target="_self">North-Bound</a> <font color="Maroon">p</font>,<font color="Maroon">C</font></span>)</span>,<span class="p1">(<span class="default"><a href="jordan18.html#K2" target="_self">South-Bound</a> <font color="Maroon">p</font>,<font color="Maroon">C</font></span>)</span> is <a href="sppol_1.html#V2">vertical</a>
 <b>by </b><i><a class="ref" href="sppol_1.html#T37">SPPOL_1:37</a></i>;<br/>


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